Firefox - Upgrade JavaScript Console Extension

This extension adds a lot of necessary functions to the Firefox JavaScript
Console window (which is renamed "Error Console") such as: sorting errors,
filtering errors by type (CSS, JS, XML) and you can even search over the
errors.

One tip, the "Clear" button isn't on the toolbar by default. To add it
you'll need to right-click the toolbar and choose "Customize". Not sure
why they didn't add the "Clear" button by default—seems like a button
that's absolutely necessary. I know it's a button I use pretty much any
time I have the JavaScript console open.